


Vanilla.

by MonsterParade



Category: Undertale (Video Game)
Genre: Fluff and Smut, Other, monster genitals, reader is trans, this is probably so schmoopy
Language: English
Status: Completed
Published: 2016-05-08
Updated: 2016-05-08
Packaged: 2018-06-07 01:43:08
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,900
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6780175
Author URL: https://archiveofourown.org/users/MonsterParade/pseuds/MonsterParade
Summary: <blockquote class="userstuff">
              <p>You love him, for all of him, and he loves you.</p>
            </blockquote>





	Vanilla.

He's always cold to the touch. Cold, waxy skin, that gives slightly under your fingers like putty. His hands shake when he touches you back, and his melted face is a flustered grey all over, his smile quirked up far too high on the left side. He is lovely. W. D. Gaster is lovely. 

[ ARE YOU NERVOUS? ] he asks, and his voice is a static gurgle that hurts your ears, even as it makes you smile. 

"Nope! Are you?" 

The both of you chuckle. That much is obvious- he finds ways to be anxious about almost everything. Poor thing. He has endeared himself to you. 

Gaster places his disembodied hands on your hips, fiddling with the edge of your boxers. Even though he has no eyes, you can tell he is avoiding yours. You lean in to kiss him on his ruined cheek. 

"We don't have to do this if you're not ready, Gaster." you tell him gently, and he all but jumps to shush you, his words coming out as a gentle whine. He clears his throat, and tries again. 

[ I AM READY! PLEASE DO NOT MISUNDERSTAND. ] he sighs. [ I SIMPLY FEAR...I WILL FRIGHTEN YOU. OR HURT YOU. AND I COULD NEVER... ]

You cut him off with a quick kiss to the lips. Not that he really has any, but the gesture is still clumsily, eagerly, returned. 

"You won't hurt me, you silly thing." you assure him, "I'm tough stuff, remember? And you're Jell-o."

You punctuate your teasing with a gentle prod to his side, and he yelps and wiggles, trying in vain to escape the poking with you straddling his waist. He grabs your hands before you have a chance to escalate to full-on tickling (his laughter is contagious). He brushes his mouth against your palms. 

[ I ADORE YOU. ]

"That's gay."

You're blushing anyway. How could you not? Just look at him. His hands are destroyed, a mess, but always gentle with you, and he takes such tender care of you, when he is the one falling apart at the seams. Even now, his breathing is labored from the effort it takes to manifest, to do this, and all for you. You want to show him your gratitude. 

"Hey. Here, um. Let me," you mutter, and give him a nervous smile before lifting your hips up out of his reach, shuffling out of your boxers and tossing them onto the floor. Gaster sucks in a heavy breath. Gingerly, flustered, you take his hand and guide it to the dark curl of hair between your legs, clasping his free hand with yours and kissing his fingers. You can feel the tension in them. Gaster twitches. 

[ SOFT, ] he notes aloud, his voice pitching upward in a familiar tone of curiosity, and you slowly allow yourself to relax, settling back down atop him and pinning his hand between your thighs. You marvel at the way the cool goop of his body moves against your bare legs. Like tiny waves. You grin at him. 

"That's all you have to say? That I'm soft?" you tease again, and gently grind down against his palm, or at least, what's left of it. He splutters helplessly. 

[ MAY I. OH DEAR. TOUCH YOU? ] he asks softly, his normally mournful voice riddled with emotion. His eyes are wide and blank, mouth open in a shapeless pant, and every so often, small drops of his skin will melt off onto yours, pooling and cooling like wax. He is dazzling. 

"Don't make me beg." you reply, and shift your hips again, allowing him room to move. Curious fingers part soft hair, to prod and stoke, coming away already damp. Your eyes almost close. 

[ CURIOUS. HOW PRECIOUS. ] Gaster remarks, almost to himself. [ YOU ARE SO UNIQUE. SO RESPONSIVE. HOW DOES THIS...WORK? ]

You snicker. 

"Find out!" you urge, and lean forward to press your cheek against his chin, delighted by the tell-tale rumble of a challenge accepted. Gaster is a scientist, after all. Trial and error is one of the things he does best. 

He moves his fingers slightly lower. Traces the edges of a small bump he finds, and carefully memorizes the gasp this earns him from you. Moves on, lower still. You're slightly worried, hoping he knows to be gentle, but then, this is your Gaster. Gentle is all he is. 

An index finger slides against your folds, gathering moisture, and Gaster marvels at it for a moment before he continues on, rubbing his fingers together. You can practically see the wheels in his head turning, can practically hear the internal monologue. All of this achingly slow touching is only making the heat in your belly worse, and you huff softly at him and give him an impatient look, hoping the brilliant scientist will understand your desire for him to hurry. 

He smiles at you, lopsided. He does understand. But you know that shit-eating grin. He won't hurry at all. 

"Gaster," you warn, about to scold him. He silences you with one finger pressed to your lips, and the other to your entrance. You inhale sharply and go quiet. 

[ MY SWEET BOY, ] Gaster coos, and starts to rub in circles, slow and slightly shaky, teasing you to make you squirm. You close your eyes and bite your lip. Every few strokes, he almost dips inside, only to move away again, and it is maddening, staining your cheeks red and making your knees quiver. Your eyes open a sliver. If he isn't going to take this seriously, then you're going to have to show him how it's done.

With the next stroke, the next almost-there, you take a breath and rock your hips downward, and force him inside of you, earning you a soft moan of surprise. He obviously hadn't been expecting that. His hands are trembling again. So are yours. 

"Gaster, my darling, light of my life, either finger-fuck me or I am going to ride your face." you threaten, and you are only half-joking. Gaster's face turns an overheated charcoal color.

[ CAN WE DO BOTH? ] he replies, cheekily, and you opt to simply roll your eyes and ignore him, trying not to smile. 

"Just move," you sigh, and sink your hips down further, enjoying the pleasant little stretch. Gaster's fingers are cool, and pleasantly long and thin, brushing lovely parts of you and making you wish all the more that he would move. Which he finally does. You groan quietly in relief. 

His movement is slow and slightly clumsy, unsure of himself and ever so gentle. He hasn't quite grasped yet how to gauge your approval, and still seems frightened of hurting you, if the worried grimace on his face is any indication. You shake your head slightly. Silly thing. 

"Gaster. You won't hurt me with one finger." you assure him, and purse your lips for a moment as he quirks his digit inside of you, his brow furrowing. 

[ ARE YOU CERTAIN? ]

"Positive! I use three, like, all the time." 

Gaster raises his eyebrows. 

[ AND YOU...ENJOY THAT? BUT THAT WOULD...STRETCH YOU, SO WIDE. ] he muses, and rubs the back of his neck with his free hand, nervous and flustered. You swallow dryly. 

"Well. Y-yeah. That's, kind of the idea." you admit. Slowly, Gaster's smirk starts to come back. 

[ OH. ] 

Bastard. You love him. 

Apparently spurred on by your confession, the newly-emboldened Gaster shifts and presses another finger into you without any warning, and this draws a real gasp from you, your hands moving down to both hold yourself up and clutch the bedsheets. It stings, slightly, but in a pleasant way that you are accustomed to, a way that only stirs up the fire in you. 

"Oh, Gaster!" 

Gaster breathes out, slowly and softly. His face seems to be dripping more than usual. 

[ YES? ]

"M-move, doofus." you grumble. You know he's used to your affectionate name-calling, and in fact, it earns you a smile, as well as your desire when he begins to slowly pump his fingers. 

[ IS THIS CORRECT? ] he asks, and the question is earnest despite everything, making you love him all the more for it. You mutely nod your head. Yes, perfect, actually. You slump forward, tucking your head under his chin, and close your eyes. 

He works you open this way for a while. 

There is no talk, only occasional huffs or moans of encouragement and labored breathing. At some point, one of your hands has moved to Gaster's shoulder, and now sits curled into the goo underneath it, flexing every so often when a nice spot is hit. You're starting to burn. 

"Gaster, fuck," you breathe, and he pauses curiously, tilting his head slightly to the side. 

[ ARE YOU HURTING? ]

"N-not even close. Gaster, do you...have anything? Down there?" you ask, and there is a tiny hint of desperation in your voice. You are certain that he can make you come with just his fingers, but you have an ulterior motive. You want to make him squirm the way he's making you. You want to return the favor. 

Gaster gives a huff of embarrassment. 

[ I-I, WELL. YES AND NO? ] he replies quietly. He has stopped moving his fingers, now. You blink. 

"Explain?" you ask. 

Gaster sighs, and pulls his fingers out of you. You could almost weep for the loss. But this was more important, now. 

[ WELL. HERE... ] he begins, sounding faintly mortified, and gestures to a patch of ooze low on his body that looks exactly the same as the rest of it, save a slight grey-ish tinge that hadn't been there before. You stare, intrigued. 

"Wwwwhat am I looking at, exactly?" you inquire, not unkindly, and Gaster groans, avoiding your gaze. 

[ YOU MAY. TOUCH IT. ...PLEASE. ]

Well, no reason not to. Eagerly, you reach out and brush your fingertips over the greyish patch, expecting the usual goop, only to find...that they pass straight through, dipping into what feels only like cold air. Gaster hisses loudly. 

[ OH, MY. ] he gulps, and you raise your eyebrows in delighted confusion, waggling the three fingers that have sunken into the strange patch. Gaster shakily clutches onto the shirt you are still wearing. 

"Is this your vagina?" you ask bluntly. Gaster chokes a little. 

[ IT IS THE VOID. ] he answers, mortified. 

You make the only obvious connection. 

"Voidgina." 

[ *NAME*! ]

You laugh, tickled both by your own pun and Gaster's reaction, and move in to kiss him, rubbing his shoulder soothingly with your free hand. He leans into you, and closes his eyes. 

[ PLEASE, MOVE. ] he urges, and despite your recent desire to get some payback, you just don't have it in you to deny the poor guy, after everything he's been through. He deserves a nice time. 

You nod, and slip your fingers further into him. He moans. 

The void around your digits is cold, and slightly wet, like the rest of him, and as you slowly stretch and explore, you find that it seems to have no boundaries, continuing on in every direction you try, even when you are certain you should have bumped into some part of him by now. Gaster is breathing heavily against you. 

"Does this end?" you ask, waggling your fingers, unsure of what would feel best in this situation. Gaster huffs, and quivers. 

[ I DON'T KNOW. I HAVE NOT DONE MUCH...EXPERIMENTATION. IN THIS REGARD. ]

You smile your best, sweetest smile. Gaster gulps. 

"I guess I'll just have to find out, then!" you exclaim, and watch his face darken again, turning ashen in embarrassment. You curl your fingers. 

"Tell me if anything gets uncomfortable, okay? I'm serious." you add. Intrigued and a little frightened by the change in your tone, Gaster nods, slowly, and then moans in shock as you thrust your whole hand into the void, just to see what would happen. Gaster's hands fly up to clutch your shoulders.

[ *NAME*, *NAME*! ] he gasps, and his whole form shivers, his mouth open wide in what you hope is pleasure. You are burning up just looking at him. 

"Good?" you ask, a little worried. He nods quickly. 

[ AGAIN. ] he all but demands, and tacks a weak little, [ PLEASE ] onto the end. You giggle. Oh, darling. You are all too happy to give him what he asks for. 

The two of you remain like this for a time, Gaster slowly seeming to melt into the mattress under your attentions and your hand slowly starting to ache from the cold around it, Gaster's soft cries creating a melody for you to work to. You are so intent upon what you are doing that you don't notice the change in Gaster until he is shaking you, his breath short and fast. It is getting harder to pull your hand out. 

[ I AM, I THINK, I CANNOT LAST MUCH LONGER. ] he stammers, and one look at his desperate face is enough to make your heart ache for him. You slow to a stop. 

"Do you want me to finish?" you ask, and cup his cheek with your hand, giving him a little kiss where his nose should be. Then, to your surprise, Gaster draws in a breath and shakes his head. 

[ NO. NOT YET. I...HAVE AN IDEA. ]

Oooh. That was always fun.

"What is it?" you ask curiously, and Gaster sits up without warning, gently grabbing your wrist and pulling your hand out of him. With it comes a long string of goo, which Gaster quickly cleans off of you, flustered to the point of almost being purple in the face. 

[ L-LIE DOWN. ] he commands, and you lay back without complaint, curious as to what he has in mind. You'll tease him about the goo later. 

Without another word, Gaster shuffles onto his hands and 'knees' and turns himself around, and it clicks for you about an instant before he settles down, and your face is pressed up into the void. You are glad you can't see yourself right now. You are certain that your cheeks must be scarlet. 

"Mmph!" you exclaim, embarrassed but delighted by this turn of events, and you do the only obvious thing, poking your tongue out of your mouth and giving a curious lick. You almost laugh. Bizarrely, the void tastes like vanilla. 

Above you, you can hear Gaster gasp, and you get in another good lick before he manages to distract you with something of his own- something very long and very hot, dragging over your folds and slipping into you with an obscene squelching sound. Your hips buck upwards of their own accord. 

Eyes closed tightly, you pause to pant against Gaster as he starts to work you over, and you can feel his smile against you, drool and goop and all manner of things dripping down your thighs. This is undeniably the hottest thing that has ever happened to you. You knot your hands into the blanket. 

With a fair amount of effort, you manage to focus yourself enough to get back to pleasuring Gaster, but he is now pursuing you with the single-mindedness of a scientist conducting an experiment, and despite his own moaning, you are on a much faster track to your messy peak. You grit your teeth and whine. 

Above you, Gaster seems to have finally remembered that bump he'd found before, when he had first begun to touch you, and, damningly, he returns to your clit and presses his lips to it, dragging his tongue over it in sloppy circles. You scrunch your eyes closed tighter. 

Maybe you can hold off. Maybe you can fight it somehow, which is not something you've ever tried, but it must be possible, right? Maybe you- maybe you can- ah, fuck. 

"Ga-Gaster, Gaster- yes, fuck me, please, Gaster," you stammer, rocking your hips, and you hear Gaster exhale shakily as he continues without mercy, not seeming to mind that you've stopped pleasuring him to moan as your climax approaches. It's a steady climb to the peak, fire burning in your belly, and as you teeter on the edge, you curl your toes and try to stave it off, stretch out this incredible feeling just a little bit longer- 

Gaster slams two fingers into you. You are helpless now, and can only whimper his name as you come, pleasure hitting a fever pitch and body tightening up as your orgasm sweeps through you. Gaster works you through it diligently, and draws it out as long as he can, fucking you open and sucking your clit until you are so over-stimulated it is painful. Then he finally draws back, and allows you to collapse onto the mattress, in a haze of bliss. That was the best orgasm you'd ever had, hands down. 

Gaster slides off of you, and sits down on his knees, turning around to face you. You cover yours eyes in embarrassment. His face is slick with your fluids, and a long, tapered tongue is hanging out of his mouth, dripping onto the bed. He looks almost as bedraggled as you imagine you do. 

[ I LOVE YOU, MY BOY. ] he hums sweetly, and pulls his tongue back into his mouth, using the corner of the blanket to clean his face and make himself once again presentable. You reach out to hold his hand. 

"I love you too," you sigh, and try not to let your grin betray you until your other hand can sneak, sneak downwards and...

[ OH!!! *NAME*!! ]


End file.
